pcre32: Add 32-bit library
Create libpcre32 that operates on 32-bit characters (UTF-32).
This turned out to be surprisingly simple after the UTF-16 support
was introduced; mostly just extra ifdefs and adjusting and adding
some tests.

General spring-clean of EBCDIC-related issues in the code, which had decayed
over time. Also the documentation. Added one test that can be run in an ASCII
world to do a little testing of EBCDIC-related things.

Typos in PrepareRelease; include 16-bit in make distcheck; fix RunTest and
RunGrepTest when building in non-source directory; problem in pcretest when no
UTF or 16-bit support; other tidies consequent on building a tarball.

Refactoring to reduce stack usage for possessively quantified subpatterns. Also
fixed a number of bugs related to repeated subpatterns. Some further tidies
consequent on the removal of OP_OPT are also in this patch.

(1) Move internal flags out of the options field, to make room.
(2) \r and \n must be explicit to trigger the special CRLF handline exception.
(3) (?J) at the start now sets JCHANGED as well as DUPNAMES.

Applied Bob and Daniel's patches to convert the build system to automake. Added
the maintain directory, containing files that are used for maintenance, but are
not distributed. This is an intermediate step.